During the past 60 years, Electron Energy Loss Spectroscopy (EELS) has become a popular tool for characterization of the composition and behavior of nanoscale regions of heterogeneous materials. Useful spectral features include atomic core loss edges in the 100-1000 eV range; bulk and surface plasmons at 1-30 eV energies; interband transitions from 1-10 eV energies; optical resonances in the 0.25-5 eV energies; and recently accessible, vibrational and phonon modes in the 10-200 meV range. Extension of these measurements to the atomic scale in nanostructures reveals a rich set of excited state interactions -- most obviously at optical energies in the form of polariton coupling that produces strongly shifted resonance energies and new symmetries which are capable of strongly coupling the interior of a nanostructure to external photon fields. These studies have been enabled by the Scanning Transmission Electron Microscope, (STEM) that can produce an Angstrom-sized probe of keV electrons to access both bulk, surface and "aloof" excitations within structures ranging from atomic to molecular to nanoscale in size. I will discuss a little history, some surprising results from my involvment in the field, and speculate on the future potential for this technique.
ABOUT THE SPEAKER
Philip E. Batson is a Distinguished Research Professor at the Institute for Advanced Materials, Devices and Nanotechnology, Rutgers University, with appointments in Physics, and Materials Science, after retirement from the IBM Thomas J. Watson Research Center in 2009. His education was at Cornell University, receiving the Ph.D. in 1976. After post-doctoral work at the Cavendish Laboratory, he moved to IBM in 1978 where he pioneered spatially resolved Electron Energy Loss Spectroscopy in the Scanning Transmission Electron Microscope, with studies of surface plasmon scattering in metal nanoparticle systems in the 1980’s. Later, using equipment built at IBM, he explored local electronic structure in Si-Ge based materials, obtained from detailed shapes of the Si 2p core loss excitation. In 2002, he demonstrated for the first time sub-Angstrom spatial resolution using the first aberration correction electron optics from Nion Microscopes, and used this capability to investigate lateral dielectric forces in sub-nanometer sized metal particles. At Rutgers he has recently begun exploring milli-eV energy excitations using a monochromated STEM. He is a Fellow of the American Physical Society and the Microscopy Society of America.